1. Field of the Invention
The present invention relates to a variable gain amplifier, and more particularly, to a CMOS variable gain amplifier with low power consumption characteristics, which can operate at a low supply voltage.
2. Background of the Related Art
Performance parameters of VGA, that must be considered in designing a CMOS variable gain amplifier (hereinafter called ‘CMOS VGA’) may include maximization of signal to noise ratio (S/N ratio) for a desired signal value, a frequency bandwidth, low distortion, a low input noise characteristic, the input signal that guarantees a target linearity, a noise characteristic, a control voltage signal, a gain control characteristic (exponential gain characteristic), and the like.
Furthermore, parameters that must be considered in designing the CMOS VGA may include dependency on temperature and power supply voltage by the CMOS characteristic. In particular, it is not easy to design the CMOS circuit having an operating frequency range of over 100 MHz in view of device technology characteristics. Furthermore, the value of the input/output signal is limited due to limitations in reduction of the threshold voltage in the MOS device. It is thus difficult to expect a smooth operation for a low supply power. As a result, it is difficult to implement the CMOS VGA with a low power consumption characteristic at the low voltage.